Idea Transcript
BIG IDEAS
M AT H
®
A Bridge to Success
Ron Larson Laurie Boswell
®
Erie, Pennsylvania BigIdeasLearning.com
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Algebraic Expressions and Properties
3
3 3.1 Algebraic Algeb l b Expressions 3.2 Writing Expressions 3.3
Properties of Addition and Multiplication
3.4 The Distributive Property
1 2 3 4 5 6
1 1 2 3 4 5 6
6 2 3 4 5 5 6 2 3 4 10 12 8 4 6 18 15 6 9 12 20 24 16 12 8 30 10 15 20 25 36 0 3 12 18 24
5, 36563 ow that 5 n k u o y “Did Þ 6 4 5?” but 5 4 6
“Descartes, evaluate this expression when x 5 2 to determin e the number of cat treats you are going to eat today.”
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1 2 3 4 5 6
1 1 2 3 4 5 6
6 2 3 4 5 6 5 2 3 4 10 12 8 6 4 18 6 9 12 15 24 20 16 8 12 30 25 20 15 10 0 36 3 24 18 12
n ke additio erations li p o ty li in a a u rt q “Only ce reserve e und.” lication p and multip ch the numbers aro it sw when you
“Remember that you eva luate an algebraic expression by substituting the value of x into the expression.”
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x
0
1
2
4+x
4
5
6
What You Learned Before Interpreting Numerical Expressions
“Great! Yo u’re u Let’s keep p to x = 2. going.”
Example 1 Write a sentence interpreting the expression i 3 × (19,762 (19 762 + 418). 418) 3 × (19,762 + 418) is 3 times as large as 19,762 + 418.
Example 2 Write a sentence interpreting the expression (316 + 43,449) + 5. (316 + 43,449) + 5 is 5 more than 316 + 43,449.
Example 3 Write a sentence interpreting the expression (20,008 − 752) ÷ 2. (20,008 − 752) ÷ 2 is half as large as 20,008 − 752.
Write a sentence interpreting the expression. 1. 3 × (372 + 20,967)
2. 2 × (432 + 346,322)
3. 4 × (6722 + 4086)
4. (115 + 36,372) + 6
5. (392 + 75,325) + 78
6. (352 + 46,795) + 100
7. (30,929 + 425) ÷ 2
8. (58,742 − 721) ÷ 2
9. (96,792 + 564) ÷ 3
Example 4 First:
Simplify 42 ÷ 2 + 3(9 − 5).
⋅ ⋅
42 ÷ 2 + 3(9 − 5) = 42 ÷ 2 + 3 4
Parentheses
Second: Exponents
= 16 ÷ 2 + 3 4
Third:
= 8 + 12
Multiplication and Division (from left to right)
= 20
Fourth: Addition and Subtraction (from left to right)
Simplify the expression. 10. 32 + 5(4 − 2) 3
13. 4(3 − 8) ÷ 2
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11. 3 + 4 ÷ 2
⋅
14. 3 6 − 4 ÷ 2
⋅ 12 + 7 ⋅ 3 − 24
12. 10 ÷ 5 3 15.
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3.1
Algebraic Expressions
How can you write and evaluate an expression that represents a real-life problem?
1
ACTIVITY: Reading and Re-Reading Work with a partner. a. You babysit for 3 hours. You receive $12. What is your hourly wage? ●
Write the problem. Underline the important numbers and units you need to solve the problem.
●
Read the problem carefully a second time. Circle the key word for the question.
You babysit for 3 hours. You receive $12. What is your hourly wage? ●
Write each important number or word, with its units, on a piece of paper. Write +, −, ×, ÷, and = on five other pieces of paper.
hourly wage ($ per hour)
Algebraic Expressions In this lesson, you will ● use order of operations to evaluate algebraic expressions. ● solve real-life problems.
●
Arrange the pieces of paper to answer the key word question, “What is your hourly wage?”
●
Evaluate the expression that represents the hourly wage. hourly wage =
÷
= So, your hourly wage is $
Write. Evaluate.
per hour.
b. How can you use your hourly wage to find how much you will receive for any number of hours worked?
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2
Math Practice Make Sense of Quantities What are the units in the problem? How does this help you write an expression?
ACTIVITY: Reading and Re-Reading Work with a partner. Use the strategy shown in Activity 1 to write an expression for each problem. After you have written the expression, evaluate it using mental math or some other method. a. You wash cars for 2 hours. You receive $6. How much do you earn per hour?
b. You have $60. You buy a pair of jeans and a shirt. The pair of jeans costs $27. You come home with $15. How much did you spend on the shirt?
c. For lunch, you buy 5 sandwiches that cost $3 each. How much do you spend?
d. You are running a 4500-foot race. How much farther do you have to go after running 2000 feet?
e. A young rattlesnake grows at a rate of about 20 centimeters per year. How much does a young rattlesnake grow in 2 years?
3. IN YOUR OWN WORDS How can you write and evaluate an expression that represents a real-life problem? Give one example with addition, one with subtraction, one with multiplication, and one with division.
Use what you learned about evaluating expressions to complete Exercises 4 –7 on page 115. Section 3.1
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Algebraic Expressions
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Lesson
3.1
Lesson Tutorials
An algebraic expression is an expression that may contain numbers, operations, and one or more symbols. Parts of an algebraic expression are called terms.
Key Vocabulary algebraic expression, p. 112 terms, p. 112 variable, p. 112 coefficient, p. 112 constant, p. 112
A symbol that represents one or more numbers is called a variable.
5p + 4
The numerical factor of a term that contains a variable is a coefficient.
EXAMPLE
A term without a variable is called a constant.
Identifying Parts of an Algebraic Expression
1
Identify the terms, coefficients, and constants in each expression. b. 2z2 + y + 3
a. 5x + 13
Study Tip
2z2 + y + 3
5x + 13
A variable by itself has a coefficient of 1. So, the term y in Example 1(b) has a coefficient of 1.
Terms: 5x,
Terms: 2z2, 1y,
13
Coefficient: 5 Constant:
Coefficients: 2, 13
3
1
Constant:
3
Identify the terms, coefficients, and constants in the expression. Exercises 8 –13
1. 12 + 10c
EXAMPLE
2.
1 2
15 + 3w + —
3. z2 + 9z
Writing Algebraic Expressions Using Exponents
2
Write each expression using exponents.
⋅ ⋅ ⋅
a. d d d d Because d is used as a factor 4 times, its exponent is 4.
⋅ ⋅ ⋅ 1.5 ⋅ h ⋅ h ⋅ h
So, d d d d = d 4.
b.
Because h is used as a factor 3 times, its exponent is 3.
⋅ ⋅ ⋅
So, 1.5 h h h = 1.5h3. 112
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Write the expression using exponents.
⋅⋅⋅⋅⋅
Exercises 16 –21
4. j j j j j j
⋅ ⋅ ⋅ ⋅ ⋅
9 k k k k k
5.
To evaluate an algebraic expression, substitute a number for each variable. Then use the order of operations to find the value of the numerical expression.
EXAMPLE
3
Evaluating Algebraic Expressions a. Evaluate k + 10 when k = 25. k + 10 = 25 + 10
Study Tip
Substitute 25 for k.
= 35
You can write the product of 4 and n in several ways. 4 n 4n 4(n)
⋅
Add 25 and 10.
b. Evaluate 4 n when n = 12.
⋅
⋅
⋅
4 n = 4 12 = 48
Substitute 12 for n. Multiply 4 and 12.
6. Evaluate 24 + c when c = 9. Exercises 25 –32
EXAMPLE
7. Evaluate d − 17 when d = 30.
4
Evaluating an Expression with Two Variables 2 3
Evaluate a ÷ b when a = 16 and b = —. 2 3
a ÷ b = 16 ÷ —
⋅ 32
Exercises 33 –36
2 3
Substitute 16 for a and — for b. 2 3
Multiply by the reciprocal of — , which is —.
= 24
Multiply.
Evaluate the expression when p = 24 and q = 8. 8. p ÷ q
9.
10. p − q
11.
q+p pq
Section 3.1
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3 2
= 16 —
Algebraic Expressions
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EXAMPLE
Evaluating Expressions with Two Operations
5
a. Evaluate 3x − 14 when x = 5. 3x − 14 = 3(5) − 14
Substitute 5 for x.
= 15 − 14
Using order of operations, multiply 3 and 5.
=1
Subtract 14 from 15.
b. Evaluate z 2 + 8.5 when z = 2. z 2 + 8.5 = 22 + 8.5
Substitute 2 for z.
= 4 + 8.5
Using order of operations, evaluate 22.
= 12.5
Add 4 and 8.5.
Evaluate the expression when y = 6. 12. 5y + 1
Exercises 43–51
EXAMPLE
13. 30 − 24 ÷ y
14. y 2 − 7
15. 1.5 + y 2
Real-Life Application
6
You are saving money to buy a skateboard. You begin with $45 and you save $3 each week. The expression 45 + 3w gives the amount of money you save after w weeks. a. How much will you have after 4 weeks, 10 weeks, and 20 weeks? b. After 20 weeks, can you buy the skateboard? Explain. Substitute the given number of weeks for w.
a.
Number of Weeks, w
45 + 3w
Amount Saved
4
45 + 3(4)
45 + 12 = $57
10
45 + 3(10)
45 + 30 = $75
20
45 + 3(20)
45 + 60 = $105
b. After 20 weeks, you have $105. So, you cannot buy the $125 skateboard.
16. WHAT IF? In Example 6, the expression for how much money you have after w weeks is 45 + 4w. Can you buy the skateboard after 20 weeks? Explain.
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Exercises
3.1
Help with Homework
1. WHICH ONE DOESN’T BELONG? Which expression does not belong with the other three? Explain your reasoning.
⋅
2x + 1
3(4) + 5
5w c
y÷z
2. NUMBER SENSE Which step in the order of operations is first? second? third? fourth? Add or subtract from left to right. Evaluate terms with exponents.
Multiply or divide from left to right. Perform operations in parentheses.
3. NUMBER SENSE Will the value of the expression 20 − x increase, decrease, or stay the same as x increases? Explain. 6)=3 9+(- 3)= 3+(- 9)= 4+(- = 1) 9+(-
Write and evaluate an expression for the problem. 4. You receive $8 for raking leaves for 2 hours. What is your hourly wage? 5. Music lessons cost $20 per week. How much do 6 weeks of lessons cost? 6. The scores on your first two history tests were 82 and 95. By how many points did you improve on your second test? 7. You buy a hat for $12 and give the cashier a $20 bill. How much change do you receive? Identify the terms, coefficients, and constants in the expression. 1
8. 7h + 3 11. 2m2 + 15 + 2p 2
✗
10. 5c 2 + 7d
9. g + 12 + 9g
Terms: 2, x 2, y Coefficient: 2 Constant: none
x2 3
1 2
12. 6 + n2 + — d
13. 8x + —
14. ERROR ANALYSIS Describe and correct the error in identifying the terms, coefficients, and constants in the algebraic expression 2x 2y.
15. PERIMETER You can use the expression 2ℓ + 2w to find the perimeter of a rectangle where ℓ is the length and w is the width.
w
a. Identify the terms, coefficients, and constants in the expression. b. Interpret the coefficients of the terms. Section 3.1
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Algebraic Expressions
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Write each expression using exponents.
⋅ ⋅ 5.2 ⋅ y ⋅ y ⋅ y
19.
✗
⋅⋅⋅⋅ a ⋅a ⋅c ⋅c
⋅ ⋅ ⋅ ⋅ 21. 2.1 ⋅ x ⋅ z ⋅ z ⋅ z ⋅ z
17. g g g g g
2 16. b b b
20.
⋅ ⋅ ⋅ ⋅
3 n n n n = 4n
18. 8 w w w w
22. ERROR ANALYSIS Describe and correct the error in writing the product using exponents.
3
23. AREA Write an expression using exponents that represents the area of the square.
As I was going to St. Ives I met a man with seven wives Each wife had seven sacks Each sack had seven cats Each cat had seven kits Kits, cats, sacks, wives How many were going to St. Ives?
5d
24. ST. IVES Suppose the man in the St. Ives poem has x wives, each wife has x sacks, each sack has x cats, and each cat has x kits. Write an expression using exponents that represents the total number of kits, cats, sacks, and wives going to St. Ives.
ALGEBRA Evaluate the expression when a = 3, b = 2, and c = 12.
⋅
3 25. 6 + a 29. 12 − b 4 33. a + b
26. b 5
27. c − 1
28. 27 ÷ a
30. c + 5
31. 2a
32. c ÷ 6
34. c − a
35. —
⋅
c a
36. b c
37. ERROR ANALYSIS Describe and correct the error in evaluating the expression when m = 8. 38. LAWNS You earn 15n dollars for mowing n lawns. How much do you earn for mowing one lawn? seven lawns?
✗
⋅ ⋅
5m + 3 = 5 8 + 3 = 5 11 = 55
39. PLANT After m months, the height of a plant is 10 + 3m millimeters. How tall is the plant after eight months? three years? Copy and complete the table. 40.
x
3
6
9
41.
⋅
x
2
4
8
64 ÷ x
x 8
42. FALLING OBJECT An object falls 16t 2 feet in t seconds. You drop a rock from a bridge that is 75 feet above the water. Will the rock hit the water in 2 seconds? Explain. 116
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ALGEBRA Evaluate the expression when a = 10, b = 9, and c = 4. 5 43. 2a + 3
1 3
45. — + —
46. — + 8
47. c 2 + 6
48. a 2 − 18
49. a + 9c
50. bc + 12.3
51. 3a + 2b − 6c
24 b
Standard Rentals $3 John Smith Bob Newman
a 4
44. 4c − 7.8
52. MOVIES You rent x new releases and y standard rentals. Which expression tells you how much money you will need?
Joe Holyman
3x + 4y
7(x + y)
4x + 3y
53. WATER PARK You float 2000 feet along a “Lazy River” water ride. The ride takes less than 10 minutes. Give two examples of possible times and speeds. Illustrate the water ride with a drawing.
New Releases $4
54. SCIENCE CENTER The expression 20a + 13c is the cost (in dollars) for a adults and c students to enter a science center.
Based on a true story
a. How much does it cost for an adult? a student? Explain your reasoning. b. Find the total cost for 4 adults and 24 students. c. You find the cost for a group. Then the numbers of adults and students in the group both double. Does the cost double? Explain your answer using an example. d. In part (b), the number of adults is cut in half, but the number of students doubles. Is the cost the same? Explain your answer.
55.
The volume of the cube is equal to four times the area of one of its faces. What is the volume of the cube?
x in.
Find the value of the power. (Section 1.2) 56. 35
57. 83
58. 74
59. 28
60. MULTIPLE CHOICE Which numbers have a least common multiple of 24? (Section 1.6) A 4, 6 ○
B 2, 22 ○
C 3, 8 ○
Section 3.1
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D 6, 12 ○
Algebraic Expressions
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3.2
Writing Expressions
How can you write an expression that represents an unknown quantity?
1
ACTIVITY: Ordering Lunch Work with a partner. You use a $20 bill to buy lunch at a café. You order a sandwich from the menu board shown.
prices includ e tax
a. Complete the table. In the last column, write a numerical expression for the amount of change received. b. REPEATED REASONING Write an expression for the amount of change you receive when you order any sandwich from the menu board. Algebraic Expressions In this lesson, you will ● use variables to represent numbers in algebraic expressions. ● write algebraic expressions.
Sandwich
Price (dollars)
Change Received (dollars)
Reuben BLT Egg salad Roast beef
c. Compare the expression you wrote in part (b) with the expressions in the last column of the table in part (a). d. The café offers several side dishes, each at the same price. You order a chicken salad sandwich and two side dishes. Write an expression for the total amount of money you spend. Explain how you wrote your expression. e. The expression 20 − 4.65s represents the amount of change one customer receives after ordering from the menu board. Explain what each part of the expression represents. Do you know what the customer ordered? Explain your reasoning.
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2
ACTIVITY: Words That Imply Addition or Subtraction Work with a partner.
Math Practice
a. Complete the table.
Use Expressions
Variable
How do the key words in the phrase help you write the given relationship as an expression?
Phrase
Expression
n
4 more than a number
m
the difference of a number and 3
x
the sum of a number and 8
p
10 less than a number
n
7 units farther away
t
8 minutes sooner
w
12 minutes later
y
a number increased by 9
b. Here is a word problem that uses one of the expressions in the table. You arrive at the café 8 minutes sooner than your friend. Your friend arrives at 6:42 P.M. When did you arrive? Which expression from the table can you use to solve the problem? c. Write a problem that uses a different expression from the table.
3
ACTIVITY: Words That Imply Multiplication or Division Work with a partner. Match each phrase with an expression. the product of a number and 3
n÷3
the quotient of 3 and a number
4p
4 times a number
n 3
a number divided by 3
2m
twice a number
3÷n
⋅
4. IN YOUR OWN WORDS How can you write an expression that represents an unknown quantity? Give examples to support your explanation.
Use what you learned about writing expressions to complete Exercises 9 –12 on page 122. Section 3.2
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Writing Expressions
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Lesson
3.2
Lesson Tutorials
Some words imply math operations. Operation Key Words and Phrases
EXAMPLE
1
Addition
Subtraction
Multiplication
Division
added to plus sum of more than increased by total of and
subtracted from minus difference of less than decreased by fewer than take away
multiplied by times product of twice of
divided by quotient of
Writing Numerical Expressions Write the phrase as an expression. a. 8 fewer than 21 21 − 8
The phrase fewer than means subtraction.
b. the product of 30 and 9
⋅
30 × 9, or 30 9
EXAMPLE
2
The phrase product of means multiplication.
Writing Algebraic Expressions Write the phrase as an expression. a. 14 more than a number x
Common Error When writing expressions involving subtraction or division, order is important. For example, the quotient of a number x and 2 means x ÷ 2, not 2 ÷ x.
x + 14
The phrase more than means addition.
b. a number y minus 75 y − 75
The word minus means subtraction.
c. the quotient of 3 and a number z 3 z
3 ÷ z, or —
The phrase quotient of means division.
Write the phrase as an expression. Exercises 3–18
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1. the sum of 18 and 35
2. 6 times 50
3. 25 less than a number b
4. a number x divided by 4
5. the total of a number t and 11
6. 100 decreased by a number k
Algebraic Expressions and Properties
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EXAMPLE
3
Writing an Algebraic Expression The length of Interstate 90 from the West Coast to the East Coast is 153.5 miles more than 2 times the length of Interstate 15 from southern California to northern Montana. Let m be the length of Interstate 15. Which expression can you use to represent the length of Interstate 90? A 2m + 153.5 ○ B 2m − 153.5 ○ C 153.5 − 2m ○ D 153.5m + 2 ○
The word times means multiplication. So, multiply 2 and m.
2m + 153.5
The phrase more than means addition. So, add 2m and 153.5.
The correct answer is ○ A .
EXAMPLE
4
Real-Life Application You plant a cypress tree that is 10 inches tall. Each year, its height increases by 15 inches. a. Make a table that shows the height of the tree for 4 years. Then write an expression for the height after t years. b. What is the height after 9 years? a. The height is increasing, so add 15 each year as shown in the table.
10 in.
Year, t
Height (inches)
0
10
1
10 + 15(1) = 25
2
10 + 15(2) = 40
3
10 + 15(3) = 55
4
10 + 15(4) = 70
When t is 0, the height is 10 inches.
You can see that an expression is 10 + 15t.
So, the height after year t is 10 + 15t.
Study Tip Sometimes, like in Example 3, a variable represents a single value. Other times, like in Example 4, a variable can represent more than one value.
Exercises 27–30
b. Evaluate 10 + 15t when t = 9. 10 + 15t = 10 + 15(9) = 145 After 9 years, the height of the tree is 145 inches.
7. Your friend has 5 more than twice as many game tokens as your sister. Let t be the number of game tokens your sister has. Write an expression for the number of game tokens your friend has. 8. WHAT IF? In Example 4, what is the height of the cypress tree after 16 years?
Section 3.2
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Writing Expressions
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Exercises
3.2
Help with Homework
1. DIFFERENT WORDS, SAME QUESTION Which is different? Write “both” expressions. 12 more than x
x increased by 12
x take away 12
the sum of x and 12
2. REASONING You pay 0.25p dollars to print p photos. What does the coefficient represent?
6)=3 9+(- 3)= 3+(- 9)= 4+(- = 1) 9+(-
Write the phrase as an expression. 1
2
3. 5 less than 8
4. the product of 3 and 12
5. 28 divided by 7
6. the total of 6 and 10
7. 3 fewer than 18
8. 17 added to 15
9. 13 subtracted from a number x
10. 5 times a number d
11. the quotient of 18 and a number a
12. the difference of a number s and 6
13. 7 increased by a number w
14. a number b squared
15. the sum of a number y and 4
16. the difference of 12 and a number x
17. twice a number z
18. a number t cubed
ERROR ANALYSIS Describe and correct the error in writing the phrase as an expression. 19. the quotient of 8 and a number y
✗
20. 16 decreased by a number x
✗
y 8
—
x − 16
21. DINNER Five friends share the cost of a dinner equally. a. Write an expression for the cost per person. b. Make up a total cost and test your expression. Is the result reasonable? 22. TV SHOW A television show has 19 episodes per season. a. Copy and complete the table. b. Write an expression for the number of episodes in n seasons.
Seasons
1
2
3
4
5
Episodes
Give two ways to write the expression as a phrase. 23. n + 6
122
Chapter 3
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24. 4w
25. 15 − b
26. 14 − 3z
Algebraic Expressions and Properties
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3
4 Write the phrase as an expression. Then evaluate when x = 5 and y = 20. 27. 3 less than the quotient of a number y and 4
28. the sum of a number x and 4, all divided by 3
29. 6 more than the product of 8 and a number x
30. the quotient of 40 and the difference of a number y and 16
31. MODELING It costs $3 to bowl a game and $2 for shoe rental. a. Make a table for the cost of up to 5 games. b. Write an expression for the cost of g games. c. Use your expression to find the cost of 8 games.
32. PUZZLE Florida has 8 less than 5 times the number of counties in Arizona.
Georgia has 25 more than twice the number of counties in Florida.
a. Write an expression for the number of counties in Florida. b. Write an expression for the number of counties in Georgia. c. Arizona has 15 counties. How many do Florida and Georgia have? 33. PATTERNS There are 140 people in a singing competition. The graph shows the results for the first five rounds.
Contestants after each round
Singing Competition
a. Write an expression for the number of people after each round. b. How many people compete in the ninth round? Explain your reasoning.
150 125 100
110
75
95
80
50
65
25 0
1
2
3
4
5
Round
34. NUMBER SENSE The difference between two numbers is 8. The lesser number is a. Write an expression for the greater number. 35.
125
One number is four times another. The greater number is x. Write an expression for the lesser number.
Evaluate the expression. (Skills Review Handbook) 36. 8 + (22 + 15)
37. (13 + 9) + 37
38. (13 × 6) × 5
39. 4 × (7 × 5)
40. MULTIPLE CHOICE A grocery store is making fruit baskets using 144 apples, 108 oranges, and 90 pears. Each basket will be identical. What is the greatest number of fruit baskets the store can make using all the fruit? (Section 1.5) A 6 ○
B 9 ○
C 16 ○
Section 3.2
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D 18 ○
Writing Expressions
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3
Study Help Graphic Organizer
You can use an information wheel to organize information about a topic. Here is an example of an information wheel for identifying parts of an algebraic expression.
In 5p + the alge b 4, 5 p an raic exp r d4 are t ession he t erm s.
on essi . r p x e nt braic oefficie e g l ea ac In th 4, 5 is 5p +
ion ress p x e le. ic ebra a variab g l a e s In th + 4, p i 5p
Identifying parts of an algebraic expression
In th e 5p + algebrai c 4, 4 is a express io cons tant n .
Make information wheels to help you study these topics. 1. evaluating algebraic expressions 2. writing algebraic expressions After you complete this chapter, make information wheels for the following topics. 3. Commutative Properties of Addition and Multiplication 4. Associative Properties of Addition and Multiplication 5. Addition Property of Zero 6. Multiplication Properties of Zero and One
“My information wheel for Fluffy has matching adjectives and nouns.”
7. Distributive Property 8. factoring expressions
124
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Quiz Q uiz
3.1–3.2 1.1–1.3
Progress Check
Identify the terms, coefficients, and constants of the expression. (Section 3.1) 2. 3r 2 + 4r + 8
1. 6q + 1 Write the expression using exponents.
⋅⋅⋅
(Section 3.1)
3. s s s s
⋅⋅⋅⋅⋅
4. 2 t t t t t
Evaluate the expression when a = 8 and b = 2. (Section 3.1) 5. a + 5
7. a2 − 6
6. ab
Copy and complete the table. (Section 3.1) 8.
x
x+6
9.
x
1
3
2
6
3
9
3x − 5
Write the phrase as an expression. (Section 3.2) 10. the sum of 28 and 35
11. a number x divided by 2
12. the product of a number m and 23
13. 10 less than a number a
14. COUPON The expression p − 15 is the amount you pay after using the coupon on a purchase of p dollars. How much do you pay for a purchase of $83? (Section 3.1)
Coupon Good for $15 off any purchase of $75 or more
15. AMUSEMENT PARK The expression 15a + 12c is the cost (in dollars) of admission at an amusement park for a adults and c children. Find the total cost for 5 adults and 10 children. (Section 3.1)
16. MOVING TRUCK To rent a moving truck for the day, it costs $33 plus $1 for each mile driven. (Section 3.2) a. Write an expression for the cost to rent the truck. b. You drive the truck 300 miles. How much do you pay?
Sections 3.1–3.2
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3.3
Properties of Addition and Multiplication Does the order in which you perform an operation matter?
1
ACTIVITY: Does Order Matter? Work with a partner. Place each statement in the correct oval. a. Fasten 5 shirt buttons. c. Fill and seal an envelope. e. Put on your shoes.
b. Put on a shirt and tie. d. Floss your teeth. f. Chew and swallow.
Order Matters
Order Doesn’t Matter
Think of three math problems using the four operations where order matters and three where order doesn’t matter.
Commute When you commute the positions of two stuffed animals on a shelf,
you switch their positions.
Equivalent Expressions In this lesson, you will ● use properties of operations to generate equivalent expressions.
2
ACTIVITY: Commutative Properties Work with a partner. a. Which of the following are true? ? 3+5=5+3 ? 9×3=3×9
? 3−5=5−3 ? 9÷3=3÷9
b. The true equations show the Commutative Properties of Addition and Multiplication. Why do you think they are called commutative? 126
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Associate And sometimes you associate with the other.
You have two best friends. Sometimes you associate with one of them.
3
Math Practice
ACTIVITY: Associative Properties Work with a partner.
Use Counterexamples What do the false equations tell you about the Associative Properties?
a. Which of the following are true? ? 8 + (3 + 1) = (8 + 3) + 1 ? 12 × (6 × 2) = (12 × 6) × 2
? 8 − (3 − 1) = (8 − 3) − 1 ? 12 ÷ (6 ÷ 2) = (12 ÷ 6) ÷ 2
b. The true equations show the Associative Properties of Addition and Multiplication. Why do you think they are called associative?
4. IN YOUR OWN WORDS Does the order in which you perform an operation matter? Give examples to support your explanation. 5. MENTAL MATH Explain how you can add the sum in your head.
11 + 7 + 12 + 13 + 8 + 9 6. SECRET CODE The creatures on a distant planet use the symbols ■ , ◆ , ★ , and ● for the four operations.
a. Use the codes to decide which symbol represents addition and which symbol represents multiplication. Explain your reasoning. 3● 4=4● 3 3★4=4★3 2 ● (5 ● 3) = (2 ● 5) ● 3 2 ★ (5 ★ 3) = (2 ★ 5) ★ 3 0● 4=0 0★4=4 b. Make up your own symbols for addition and multiplication. Write codes using your symbols. Trade codes with a classmate. Decide which symbol represents addition and which symbol represents multiplication.
Use what you learned about the properties of addition and multiplication to complete Exercises 5 – 8 on page 130. Section 3.3
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Lesson
3.3
Lesson Tutorials
Expressions with the same value, like 12 + 7 and 7 + 12, are equivalent expressions. You can use the Commutative and Associative Properties to write equivalent expressions.
Key Vocabulary equivalent expressions, p. 128
Commutative Properties Changing the order of addends or factors does not change the sum or product.
Words
Numbers
5+8=8+5
⋅
Algebra
⋅
a+b=b+a
⋅
5 8=8 5
⋅
a b=b a
Associative Properties Changing the grouping of addends or factors does not change the sum or product.
Words
Numbers
(7 + 4) + 2 = 7 + (4 + 2)
⋅ ⋅
⋅ ⋅
(7 4) 2 = 7 (4 2) Algebra
(a + b) + c = a + (b + c)
⋅ ⋅
⋅ ⋅
(a b) c = a (b c)
EXAMPLE
1
Using Properties to Write Equivalent Expressions a. Simplify the expression 7 + (12 + x).
Study Tip
7 + (12 + x) = (7 + 12) + x
One way to check whether expressions are equivalent is to evaluate each expression for any value of the variable. In Example 1(a), use x = 2. 7 + (12 + x) = 19 + x
= 19 + x
21 = 21
✓
Add 7 and 12.
b. Simplify the expression (6.1 + x) + 8.4. (6.1 + x) + 8.4 = (x + 6.1) + 8.4
?
7 + (12 + 2) = 19 + 2
Associative Property of Addition
Commutative Property of Addition
= x + (6.1 + 8.4)
Associative Property of Addition
= x + 14.5
Add 6.1 and 8.4.
c. Simplify the expression 5(11y).
⋅
5(11y) = (5 11)y
Associative Property of Multiplication
= 55y
Multiply 5 and 11.
Simplify the expression. Explain each step. Exercises 5 – 8
128
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1. 10 + (a + 9)
2.
( ) 2 3
1 2
c+— +—
3.
5(4n)
Algebraic Expressions and Properties
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Addition Property of Zero Words
The sum of any number and 0 is that number.
Numbers
7+0=7
Algebra
a+0=a
Multiplication Properties of Zero and One Words
The product of any number and 0 is 0. The product of any number and 1 is that number.
Numbers
EXAMPLE
2
⋅ 4 ⋅1 = 4
9 0=0
Algebra
⋅ a ⋅1 = a
a 0=0
Using Properties to Write Equivalent Expressions
⋅ ⋅
a. Simplify the expression 9 0 p.
⋅ ⋅
⋅ ⋅ = 0 ⋅p = 0
9 0 p = (9 0) p
Associative Property of Multiplication Multiplication Property of Zero
⋅⋅
b. Simplify the expression 4.5 r 1.
⋅⋅
⋅ ⋅ = 4.5 ⋅ r
4.5 r 1 = 4.5 (r 1)
Associative Property of Multiplication Multiplication Property of One
= 4.5r
EXAMPLE
Common Error You and six friends are on the team, so use the expression 7x, not 6x, to represent the cost of the T-shirts.
3
Real-Life Application You and six friends play on a basketball team. A sponsor paid $100 for the league fee, x dollars for each player’s T-shirt, and $68.25 for trophies. Write an expression for the total amount the sponsor paid. Add the league fee, the cost of the T-shirts, and the cost of the trophies. 100 + 7x + 68.25 = 7x + 100 + 68.25 = 7x + 168.25
Commutative Property of Addition Add 100 and 68.25.
An expression for the total amount is 7x + 168.25.
Simplify the expression. Explain each step. Exercises 9 – 23
⋅ ⋅
4. 12 b 0
5.
⋅ ⋅
1 m 24
6.
(t + 15) + 0
7. WHAT IF? In Example 3, your sponsor paid $54.75 for trophies. Write an expression for the total amount the sponsor paid.
Section 3.3
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Exercises
3.3
Help with Homework
1. NUMBER SENSE Write an example of a sum of fractions. Show that the Commutative Property of Addition is true for the sum. 2. OPEN-ENDED Write an algebraic expression that can be simplified using the Associative Property of Addition. 3. OPEN-ENDED Write an algebraic expression that can be simplified using the Associative Property of Multiplication and the Multiplication Property of One. 4. WHICH ONE DOESN’T BELONG? Which statement does not belong with the other three? Explain your reasoning. 7 + (x + 4) = 7 + (4 + x)
(3 + b) + 2 = (b + 3) + 2
9 + (7 + w) = (9 + 7) + w
(4 + n) + 6 = (n + 4) + 6
6)=3 9+(- 3)= 3+(- 9)= 4+(- = 1) 9+(-
Tell which property the statement illustrates. 1
2
⋅ ⋅ 4 ⋅ (x ⋅ 10) = (4 ⋅ x) ⋅ 10
5. 5 p = p 5
6. 2 + (12 + r) = (2 + 12) + r
7.
8. x + 7.5 = 7.5 + x
⋅
10. a 1 = a
9. (c + 2) + 0 = c + 2
11. ERROR ANALYSIS Describe and correct the error in stating the property that the statement illustrates.
✗
(7 + x) + 3 = (x + 7 ) + 3 Associative Property of Addition
Simplify the expression. Explain each step. 12. 6 + (5 + x)
13. (14 + y) + 3
14. 6(2b)
15. 7(9w)
16. 3.2 + (x + 5.1)
17. (0 + a) + 8
⋅⋅
⋅ ⋅ (3s) ⋅ 8
(
1 5
)
3 5
18. 9 c 4
19. (18.6 d ) 1
20. 3k + 4 — + 8 —
21. (2.4 + 4n) + 9
22.
23. z 0 12
⋅ ⋅
24. GEOMETRY The expression 12 + x + 4 represents the perimeter of a triangle. Simplify the expression. 25. SCOUT COOKIES A case of Scout cookies has 10 cartons. A carton has 12 boxes. The amount you earn on a whole case is 10(12x) dollars. a. What does x represent? b. Simplify the expression. 130
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⋅⋅
26. STRUCTURE The volume of the rectangular prism is 12.5 x 1.
1
a. Simplify the expression. b. Match x = 0.25, 12.5, and 144 with the object. Explain. A. siding for a house
B. ruler
x 12.5
C. square floor tile
Write the phrase as an expression. Then simplify the expression. 27. 7 plus the sum of a number x and 5 28. the product of 8 and a number y multiplied by 9 Copy and complete the statement using the specified property. Property
Statement
29.
Associative Property of Multiplication
7(2y) =
30.
Commutative Property of Multiplication
13.2 (x 1) =
31.
Associative Property of Addition
17 + (6 + 2x) =
32.
Addition Property of Zero
2 + (c + 0) =
33.
Multiplication Property of One
1 w 16 =
⋅ ⋅
⋅ ⋅
34. HATS You and a friend sell hats at a fair booth. You sell 16 hats on the first shift and 21 hats on the third shift. Your friend sells x hats on the second shift. a. Write an expression for the number of hats sold. b. The expression 37(14) + 10x represents the amount that you both earned. How can you tell that your friend was selling the hats for a discounted price? c.
You earned more money than your friend. What can you say about the value of x?
Evaluate the expression. (Section 1.3) 35. 7(10 + 4)
36. 12(10 − 1)
37. 6(5 + 10)
38. 8(30 − 5)
Find the prime factorization of the number. (Section 1.4) 39. 37
40. 144
41. 147
42. 205
43. MULTIPLE CHOICE A bag has 16 blue, 20 red, and 24 green marbles. What fraction of the marbles in the bag are blue? (Skills Review Handbook) A ○
1 5
—
B ○
4 15
—
Section 3.3
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C ○
4 11
—
D ○
11 15
—
Properties of Addition and Multiplication
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3.4
The Distributive Property
How do you use mental math to multiply two numbers?
Distribute When you distribute something to each person in a group,
you give that thing to each person in the group.
à
à
1
ACTIVITY: Modeling a Property Work with a partner. a. MODELING Draw two rectangles of the same width but with different lengths on a piece of grid paper. Label the dimensions.
Equivalent Expressions In this lesson, you will ● use the Distributive Property to find products. ● use the Distributive Property to simplify algebraic expressions.
b. Write an expression for the total area of the rectangles.
(
)+(
×
)
×
c. Rearrange the rectangles by aligning the shortest sides to form one rectangle. Label the dimensions. Write an expression for the area. ×
(
+
)
d. Can the expressions from parts (b) and (c) be set equal to each other? Explain. e. REPEATED REASONING Repeat this activity using different rectangles. Explain how this illustrates the Distributive Property. Write a rule for the Distributive Property. 132
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2
ACTIVITY: Using Mental Math Work with a partner. Use the method shown to find the product.
Math Practice
a. Sample: 23 × 6
Find Entry Points
23 × 6 120 + 18 138
How can you rewrite the larger number as the sum of two numbers so that you can use mental math?
23 is 20 + 3. Multiply 20 and 6. Multiply 3 and 6. Add.
So, 23 × 6 = 138. b. 33 × 7
c. 47 × 9
d. 28 × 5
e. 17 × 4
3
ACTIVITY: Using Mental Math Work with a partner. Use the Distributive Property and mental math to find the product. a. Sample: 6 × 23 6 × 23 = 6 × (20 + 3)
Write 23 as the sum of 20 and 3.
= (6 × 20) + (6 × 3)
Distribute the 6 over the sum.
= 120 + 18
Find the products.
= 138
Add.
So, 6 × 23 = 138. b. 5 × 17
c. 8 × 26
d. 20 × 19
e. 40 × 29
25 × 39
g. 15 × 47
f.
4. Compare the methods in Activities 2 and 3. 5. IN YOUR OWN WORDS How do you use mental math to multiply two numbers? Give examples to support your explanation.
Use what you learned about the Distributive Property to complete Exercises 5–8 on page 137. Section 3.4
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Lesson
3.4
Lesson Tutorials
Key Vocabulary like terms, p. 136
Distributive Property Words
To multiply a sum or difference by a number, multiply each number in the sum or difference by the number outside the parentheses. Then evaluate.
Numbers
3(7 + 2) = 3 × 7 + 3 × 2
a(b + c) = ab + ac
Algebra
3(7 − 2) = 3 × 7 − 3 × 2
EXAMPLE
1
a(b − c) = ab − ac
Using Mental Math Use the Distributive Property and mental math to find 8 × 53. 8 × 53 = 8(50 + 3)
EXAMPLE
2
Write 53 as 50 + 3.
= 8(50) + 8(3)
Distributive Property
= 400 + 24
Multiply.
= 424
Add.
Using the Distributive Property 1 2
3 4
Use the Distributive Property to find — × 2 —. 1 2
3 4
( ) ( ) ( ) 1 2
3 4
3 4
1 2
1 2
3 4
Rewrite 2 — as the sum 2 + —.
— × 2— = — × 2 + —
3 4
= —×2 + —×—
Distributive Property
3 8
=1+—
Multiply.
3 8
= 1—
Add.
Use the Distributive Property to find the product. Exercises 5 –16
1. 5 × 41
2.
9 × 19
3.
6(37)
1 2
5.
— × 4—
1 5
6.
— × 3—
2 3
4. — × 1—
134
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1 4
2 7
3 4
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EXAMPLE
3
Simplifying Algebraic Expressions Use the Distributive Property to simplify the expression. a. 4(n + 5) 4(n + 5) = 4(n) + 4(5)
Distributive Property
= 4n + 20
Study Tip
Multiply.
b. 12(2y − 3)
You can use the Distributive Property when there are more than two terms in the sum or difference.
12(2y − 3) = 12(2y) − 12(3) = 24y − 36
Distributive Property Multiply.
c. 9(6 + x + 2) 9(6 + x + 2) = 9(6) + 9(x) + 9(2)
Distributive Property
= 54 + 9x + 18
Multiply.
= 9x + 54 + 18
Commutative Property of Addition
= 9x + 72
Add 54 and 18.
Use the Distributive Property to simplify the expression. 7. 7(a + 2)
Exercises 17 –32
EXAMPLE
4
8.
3(d − 11)
9.
7(2 + 6 − 4d)
Real-Life Application José is x years old. His brother, Felipe, is 2 years older than José. Their aunt, Maria, is three times as old as Felipe. Write and simplify an expression that represents Maria’s age in years. Name
Description
Expression
José
He is x years old.
Felipe
He is 2 years older than José. So, add 2 to x.
Maria
She is three times as old as Felipe. So, multiply 3 and (x + 2).
3(x + 2) = 3(x) + 3(2)
x x+2 3(x + 2)
Distributive Property
= 3x + 6
Multiply.
Maria’s age in years is represented by the expression 3x + 6.
Section 3.4
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10. Alexis is x years old. Her sister, Gloria, is 7 years older than Alexis. Their grandfather is five times as old as Gloria. Write and simplify an expression that represents their grandfather’s age in years.
In an algebraic expression, like terms are terms that have the same variables raised to the same exponents. Constant terms are also like terms. Like terms
5x + 19 + 2x + 2 Like terms
Use the Distributive Property to combine like terms.
EXAMPLE
5
Combining Like Terms Simplify each expression. a. 3x + 9 + 2x − 5 3x + 9 + 2x − 5 = 3x + 2x + 9 − 5
Commutative Property of Addition
= (3 + 2)x + 9 − 5
Distributive Property
= 5x + 4
Simplify.
b. y + y + y y + y + y = 1y + 1y + 1y
Multiplication Property of One
= (1 + 1 + 1)y
Distributive Property
= 3y
Add coefficients.
c. 7z + 2(z − 5y) 7z + 2(z − 5y) = 7z + 2(z) − 2(5y)
Distributive Property
= 7z + 2z − 10y
Multiply.
= (7 + 2)z − 10y
Distributive Property
= 9z − 10y
Add coefficients.
Simplify the expression. Exercises 39 –53
136
Chapter 3
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11. 8 + 3z − z
12.
3(b + 5) + b + 2
Algebraic Expressions and Properties
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Exercises
3.4
Help with Homework
1. WRITING One meaning of the word distribute is “to give something to each member of a group.” How can this help you remember the Distributive Property? 2. OPEN-ENDED Write an algebraic expression in which you use the Distributive Property and then the Associative Property of Addition to simplify. 3. WHICH ONE DOESN’T BELONG? Which expression does not belong with the other three? Explain your reasoning. 2(x + 2)
5(x − 8)
⋅
8(9 − x)
4 + (x 4)
4. Identify the like terms in the expression 8x + 1 + 7x + 4. 6)=3 9+(- 3)= 3+(- 9)= 4+(- = 1) 9+(-
Use the Distributive Property and mental math to find the product. 1
5. 3 × 21
6. 9 × 76
9. 18 × 52
10. 8 × 27
7. 12(43)
8. 5(88)
11. 8(63)
12. 7(28)
Use the Distributive Property to find the product. 1 4
2 7
2 13. — × 2 —
5 6
2 5
14. — × 2 —
5 9
2 15
1 2
15. — × 4 —
5 8
16. — × 5 —
Use the Distributive Property to simplify the expression. 3 17. 3(x + 4)
18. 10(b − 6)
19. 6(s − 9)
20. 7(8 + y)
21. 8(12 + a)
22. 9(2n + 1)
23. 12(6 − k)
24. 18(5 − 3w)
25. 9(3 + c + 4)
26. 7(8 + x + 2)
27. 8(5g + 5 − 2)
28. 6(10 + z + 3)
29. 4(x + y)
30. 25(x − y)
31. 7(p + q + 9)
32. 13(n + 4 + 7m)
✗
33. ERROR ANALYSIS Describe and correct the error in rewriting the expression.
6(y + 8) = 6y + 8
34. ART MUSEUM A class of 30 students visits an art museum and a special exhibit while there. a. Use the Distributive Property to write and simplify an expression for the cost. b. Estimate a reasonable value for x. Explain.
PRICES Child (under 5) Student Regular Senior
Museum Exhibit Free Free $x $8 $12 $4 $10 $3
c. Use your estimate for x to evaluate the original expression and the simplified expression in part (a). Are the values the same?
Section 3.4
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35. FITNESS Each day, you run on a treadmill for r minutes and lift weights for 15 minutes. Which expressions can you use to find how many minutes of exercise you do in 5 days? Explain your reasoning.
⋅
5(r + 15)
5r + 5 15
5r + 15
r (5 + 15)
36. SPEED A cheetah can run 103 feet per second. A zebra can run x feet per second. Use the Distributive Property to write and simplify an expression for how much farther the cheetah can run in 10 seconds.
UNIFORMS Your baseball team has 16 players. Use the Distributive Property to write and simplify an expression for the total cost of buying the items shown for all the players. 37.
38. or and
or
or
and
and or
Pants: $10
Belt: $x Jersey: $12
Socks: $4
Hat: $x
5 Simplify the expression. 39. 6(x + 4) + 1
40. 5 + 8(3 + x)
41. 7(8 + 4k) + 12
42. x + 3 + 5x
43. 7y + 6 − 1 + 12y
44. w + w + 5w
45. 4d + 9 − d − 8
46. n + 3(n − 1)
47. 2v + 8v − 5v
48. 5(z + 4) + 5(2 − z)
49. 2.7(w − 5.2)
50. — y + — y + y
52. 7(x + y) − 7x
53. 4x + 9y + 3(x + y)
3 4
(
2 5
)
51. — z + — + 2z
54. ERROR ANALYSIS Describe and correct the error in simplifying the expression.
✗
2 3
1 6
8x − 2x + 5x = 8x − 7x = (8 − 7)x =x
ALGEBRA Find the value of x that makes the expressions equivalent. 55. 4(x − 5); 32 − 20
56. 2(x + 9); 30 + 18
57. 7(8 − x); 56 − 21
58. REASONING Simplify the expressions and compare. What do you notice? Explain. 4(x + 6) 138
Chapter 3
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(x + 6) + (x + 6) + (x + 6) + (x + 6)
Algebraic Expressions and Properties
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GEOMETRY Write and simplify expressions for the area and perimeter of the rectangle. 60.
59.
61.
8 9
12 xà8
7
x
5
5.5 á x
62. FUNDRAISER An art club sells 42 large candles and 56 small candles. a. Use the Distributive Property to write and simplify an expression for the profit.
Price: $10 Cost: $x
b. A large candle costs $5, and a small candle costs $3. What is the club’s profit?
Price: $5 Cost: $y
Profit â Price Ź Cost
63. REASONING Evaluate each expression by (1) using the Distributive Property and (2) evaluating inside the parentheses first. Which method do you prefer? Is your preference the same for both expressions? Explain your reasoning.
(
a. 2(3.22 − 0.12)
1 2
2 3
b. 12 — + —
)
64. REASONING Write and simplify an expression for the difference between the perimeters of the rectangle and the hexagon. Interpret your answer. x 2x
2x
xá8
2x á 7 2x
xá6 x
65.
Add one set of parentheses to the expression
⋅
⋅
⋅
7 x + 3 + 8 x + 3 x + 8 − 9 so that it is equivalent to 2(9x + 10).
Evaluate the expression. (Section 2.4, Section 2.5, and Section 2.6) 66. 4.871 + 7.4 − 1.63
⋅
68. 15.3 9.1 − 4.017
67. 25.06 − 0.049 + 8.995
⋅
69. 29.24 ÷ 3.4 0.045
70. MULTIPLE CHOICE What is the GCF of 48, 80, and 96? (Section 1.5) A 12 ○
B 16 ○
C 24 ○
D 480 ○
Section 3.4
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Extension
3.4
FFactoring a Expressions Lesson Tutorials
Key Vocabulary
Factoring an Expression
factoring an expression, p. 140
Words
Writing a numerical expression or algebraic expression as a product of factors is called factoring the expression. You can use the Distributive Property to factor expressions.
Numbers
EXAMPLE
1
⋅ ⋅ 3 ⋅ 7 − 3 ⋅ 2 = 3(7 − 2)
3 7 + 3 2 = 3(7 + 2)
Algebra
ab + ac = a(b + c) ab − ac = a(b − c)
Factoring a Numerical Expression Factor 20 − 12 using the GCF.
Study Tip
Find the GCF of 20 and 12 by listing their factors.
When you factor an expression, you can factor out any common factor.
Factors of 20: 1 , 2 , 4 , 5, 10, 20 Circle the common factors.
Factors of 12: 1 , 2 , 3, 4 , 6, 12 The GCF of 20 and 12 is 4.
Write each term of the expression as a product of the GCF and the remaining factor. Then use the Distributive Property to factor the expression. 20 − 12 = 4(5) − 4(3) = 4(5 − 3)
EXAMPLE
2
Rewrite using GCF. Distributive Property
Identifying Equivalent Expressions Which expression is not equivalent to 16x + 24?
Equivalent Expressions In this extension, you will ● use the Distributive Property to produce equivalent expressions.
A 2(8x + 12) ○
B 4(4x + 6) ○
C 6(3x + 4) ○
D (2x + 3)8 ○
Each choice is a product of two factors in which one is a whole number and the other is the sum of two terms. For an expression to be equivalent to 16x + 24, its whole number factor must be a common factor of 16 and 24. Factors of 16: 1 , 2 , 4 , 8 , 16 Factors of 24: 1 , 2 , 3, 4 , 6, 8 , 12, 24
Circle the common factors.
The common factors of 16 and 24 are 1, 2, 4, and 8. Because 6 is not a common factor of 16 and 24, Choice C cannot be equivalent to 16x + 24. Check: 6(3x + 4) = 6(3x) + 6(4) = 18x + 24 ≠ 16x + 24
✗
So, the correct answer is ○ C . 140
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EXAMPLE
3
Factoring an Algebraic Expression You receive a discount on each book you buy for your electronic reader. The original price of each book is x dollars. You buy 5 books for a total of (5x − 15) dollars. Factor the expression. What can you conclude about the discount? Find the GCF of 5x and 15 by writing their prime factorizations.
⋅ 15 = 5 ⋅ 3
5x = 5 x
Circle the common prime factor.
So, the GCF of 5x and 15 is 5. Use the GCF to factor the expression. 5x − 15 = 5(x) − 5(3) = 5(x − 3)
Rewrite using GCF. Distributive Property
The factor 5 represents the number of books purchased. The factor (x − 3) represents the price of each book. This factor is a difference of two terms, showing that the price x of each book is decreased by $3. So, the factored expression shows a $3 discount for every book you buy. The original expression shows a total savings of $15.
Factor the expression using the GCF. 1. 7 + 14
2. 44 − 11
3. 18 − 12
4. 70 + 95
5. 60 − 36
6. 100 − 80
7. 84 + 28
8. 48 + 80
9. 2x + 10
10. 15x + 6
11. 26x − 13
12. 50x − 60
13. 36x + 9
14. 14x − 98
15. 10x − 25y
16. 24y + 88x
17. REASONING The whole numbers a and b are divisible by c. Is a + b divisible by c ? Is b − a divisible by c ? Explain your reasoning. 18. OPEN-ENDED Write five expressions that are equivalent to 8x + 16. 19. GEOMETRY The area of the parallelogram is (4x + 16) square feet. Write an expression for the base.
4 ft
20. STRUCTURE You buy 37 concert tickets for $8 each, and then sell all 37 tickets for $11 each. The work below shows two ways you can determine your profit. Describe each solution method. Which do you prefer? Explain your reasoning. profit = 37(11) − (37)8 = 407 − 296 = $111
profit = 37(11) − (37)8 = 37(11 − 8) = 37(3) = $111 Extension 3.4
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Quiz
3.3–3.4
Progress Check
Tell which property the statement illustrates. (Section 3.3)
⋅
⋅
1. 3.5 z = z 3.5
2. 14 + (35 + w) = (14 + 35) + w
Simplify the expression. Explain each step. (Section 3.3)
⋅ ⋅
3. 3.2 + (b + 5.7)
4. 6 (10 k)
Use the Distributive Property and mental math to find the product. (Section 3.4) 5. 6 × 49
6. 7 × 86
Use the Distributive Property to simplify the expression. (Section 3.4) 7. 5(x − 8)
8. 7( y + 3)
Simplify the expression. (Section 3.4) 9. 6q + 2 + 3q + 5
10. 4r + 3(r − 2)
Factor the expression using the GCF. (Section 3.4) 11. 12 + 21
12. 16x − 36
13. GEOMETRY The expression 18 + 7 + (18 + 2x) + 7 represents the perimeter of the trapezoid. Simplify the expression. (Section 3.3)
18 à 2x 7
7 18
Movie Tickets Student $8 Adult $10
Snacks Candy $3 Popcorn $x
14. MOVIES You and four of your friends go to a movie and each buy popcorn. (Section 3.4)
a. Use the Distributive Property to write an expression for the total cost to buy movie tickets and popcorn. Simplify the expression. b. Choose a reasonable value for x. Evaluate the expression.
15. GEOMETRY The length of a rectangle is 16 inches, and its area is (32x + 48) square inches. Factor the expression for the area. Write an expression for the width. (Section 3.4)
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Chapter Review Vocabulary Help
Review Key Vocabulary coefficient, p. 112 constant, p. 112 equivalent expressions, p. 128
algebraic expression, p. 112 terms, p. 112 variable, p. 112
like terms, p. 136 factoring an expression, p. 140
Review Examples and Exercises 3.1
Algebraic Expressions
(pp. 110–117)
a. Evaluate a ÷ b when a = 48 and b = 8. a ÷ b = 48 ÷ 8
Substitute 48 for a and 8 for b.
=6
Divide 48 by 8.
b. Evaluate y 2 − 14 when y = 5. y 2 − 14 = 52 − 14
Substitute 5 for y.
= 25 − 14
Using order of operations, evaluate 52.
= 11
Subtract 14 from 25.
Evaluate the expression when x = 20 and y = 4. 1. x ÷ 5
2. y + x
3. 8y − x
4. GAMING In a video game, you score p game pointss and b triple bonus points. An expression for your score is p + 3b. What is your score when you earn 245 game points and 20 triple bonus points?
3.2
Writing Expressions
(pp. 118–123)
Write the phrase as an expression. a. a number z decreased by 18 z − 18
The phrase decreased by means subtraction. i
b. the sum of 7 and the product of a number x and 12 7 + 12x
The phrase sum of means addition. The phrase product of means multiplication.
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Write the phrase as an expression. 5. 11 fewer than a number b
6. the product of a number d and 32
7. 18 added to a number n
8. a number t decreased by 17
9. BASKETBALL Your basketball team scored 4 fewer than twice as many points as the other team. a. Write an expression for the number of points your team scored. b. The other team scored 24 points. How many points did your team score?
3.3
Properties of Addition and Multiplication
(pp. 126–131)
a. Simplify the expression (x + 18) + 4. (x + 18) + 4 = x + (18 + 4)
Associative Property of Addition
= x + 22
Add 18 and 4.
b. Simplify the expression (5.2 + a) + 0. (5.2 + a) + 0 = 5.2 + (a + 0) = 5.2 + a
Associative Property of Addition Addition Property of Zero
⋅⋅
c. Simplify the expression 36 r 1.
⋅⋅
⋅ ⋅ = 36 ⋅ r
36 r 1 = 36 (r 1)
Associative Property of Multiplication Multiplication Property of One
= 36r
Simplify the expression. Explain each step. 10. 10 + (2 + y)
11. (21 + b) + 1
12. 3(7x)
13. 1(3.2w)
14. 5.3 + (w + 1.2)
15. (0 + t) + 9
16. GEOMETRY The expression 7 + 3x + 4 represents the perimeter of the triangle. Simplify the expression.
7
3x
4
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3.4
The Distributive Property
(pp. 132–141)
a. Use the Distributive Property to simplify 3(n + 9). 3(n + 9) = 3(n) + 3(9)
Distributive Property
= 3n + 27
Multiply.
b. Simplify 5x + 7 + 3x − 2. 5x + 7 + 3x − 2 = 5x + 3x + 7− 2
Commutative Property of Addition
= (5 + 3)x + 7 − 2
Distributive Property
= 8x + 5
Simplify.
c. Factor 14x − 49 using the GCF. Find the GCF of 14x and 49 by writing their prime factorizations.
⋅ ⋅ 49 = 7 ⋅ 7
14x = 2 7 x
Circle the common prime factor.
So, the GCF of 14x and 49 is 7. Use the GCF to factor the expression. 14x − 49 = 7(2x) − 7(7)
Rewrite using GCF.
= 7(2x − 7)
Distributive Property
Use the Distributive Property to find the product. 3 4
1 3
17. — × 2 —
4 7
5 8
18. — × 4 —
1 5
10 11
19. — × 5 —
Use the Distributive Property to simplify the expression. 20. 2(x + 12)
21. 11(b − 3)
22. 8(s − 1)
23. 6(6 + y)
24. 25(z − 4)
25. 35(w − 2)
26. HAIRCUT A family of four goes to a salon for haircuts. The cost of each haircut is $13. Use the Distributive Property and mental math to find the product 4 × 13 for the total cost. Simplify the expression. 27. 5(n + 3) + 4n
28. t + 2 + 6t
29. 3z + 4 + 5z − 9
Factor the expression using the GCF. 30. 15 + 35
31. 36x − 28
32. 16x + 56y Chapter Review
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1 3
Chapter Test Test Practice
Evaluate the expression when a = 6 and b = 8. 1. 4 + a
2. a − 6
3. ab
Write the phrase as an expression. 4. twice a number x
5. 25 more than 50
6. 40 divided by 5
Simplify the expression. Explain each step. 7. 3.1 + (8.6 + m)
⋅ ⋅
8. (10 n) 7
9. 3(15w)
Use the Distributive Property to simplify the expression. 10. 4(x + 8)
11. 12( y − 5)
Simplify the expression. 12. 4(q + 2) − 6
13. 3(2 + 5r) + 11
14. s + 3s + 4s
15. 4t − 2 − 2t + 7
Factor the expression using the GCF. 16. 18 + 24
17. 40 − 16
18. 15x + 20
19. 32x − 40y
20. SOCCER GAME Playing time is added at the end of a soccer game to make up for stoppages. An expression for the length of a 90-minute soccer game with x minutes of stoppage time is 90 + x. How long is a game with 4 minutes of stoppage time?
⋅⋅
21. GEOMETRY The expression 15 x 6 represents the volume of a rectangular prism with a length of 15, a width of x, and a height of 6. Simplify the expression.
22. PARTY FAVORS You make party favors for an event. You tie 9 inches of ribbon around each party favor. Write an expression for the amount of ribbon you need for n party favors. The ribbon costs $3 for each yard. Write an expression for the total cost of the ribbon.
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3
Cumulative Assessment Test-Takin g Strateg y wering E asy Ques tions, Re lax
After Ans
1. The student council is organizing a school fair. Council members are making signs to show the prices for admission and for each game a person can play.
SCHOOL FAIR Admission Price per game
$2.00 $0.25
Let x represent the number of games. Which expression can you use to determine the total amount, in dollars, a person pays for admission and playing x games? A. 2.25
C. 2 + 0.25x
B. 2.25x
D. 2x + 0.25
“After a nsw and tr y ering easy que the hard stions, 3(4) = 1 er ones. For th relax 2. So, it is, is B.”
2. Which property does the equation below represent?
⋅
⋅
⋅
17 44 + 17 56 = 17 100 F. Distributive Property G. Multiplication Property of One
3. At a used book store, you can purchase two types of books.
H. Associative Property of Multiplication I. Commutative Property of Multiplication
Hardcover Books - $3
Paperback Books - $2
You can use the expression 3h + 2p to find the total cost for h hardcover books and p paperback books. What is the total cost, in dollars, for 6 hardcover books and 4 paperback books?
4. What is the value of 9.6 × 12.643? A. 12.13728
C . 1213.728
B. 121.3728
D. 12,137.28 Cumulative Assessment
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5. What is the value of 4.391 + 5.954? F. 9.12145
H. 9.345
G. 9.245
I . 10.345
6. Which number pair has a greatest common factor of 6? A. 18, 54
C. 30, 60
B. 30, 42
D. 36, 60
7. Properties of Addition and Multiplication are used to simplify an expression.
⋅
⋅
⋅ ⋅ ⋅ ⋅ = 36 ⋅ 23 + 64 ⋅ 23 + 64 ⋅ 10 = x ⋅ 23 + 64 ⋅ 10
36 23 + 33 64 = 36 23 + 64 33
= 36 23 + 64 (23 + 10)
= 2300 + 640 = 2940
What number belongs in place of the x? 8. Which property was used to simplify the expression? (47 × 125) × 8 = 47 × (125 × 8) = 47 × 1000 = 47,000 F. Distributive Property G. Multiplication Property of One H. Associative Property of Multiplication I. Commutative Property of Multiplication 9. What is the value of the expression below when a = 5, b = 7, and c = 6? 9b − 4a + 2c
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A. 29
C. 55
B. 31
D. 78
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10. Which equation correctly demonstrates the Distributive Property? F. a(b + c) = ab + c G. a(b + c) = ab + ac H. a + (b + c) = (a + b) + (a + c)
⋅
I. a + (b + c) = (a + b) (a + c) 3 5
1 2
11. Which expression is equivalent to 3 — ÷ 6 —? 5 18
13 2
C. — ÷ —
9 5
18 5
2 13
D. — ÷ —
A. — × —
18 5
B. — × —
6 2
2 13
12. Which number pair does not have a least common multiple of 24? F. 2, 12
H. 6, 8
G. 3, 8
I. 12, 24
13. Use the Properties of Multiplication to simplify the expression in an efficient way. Show your work and explain how you used the Properties of Multiplication. (25 × 18) × 4
14. You evaluated an expression using x = 6 and y = 9. You correctly got an answer of 105. Which expression did you evaluate? A. 3x + 6y
C. 6x + 9y
B. 5x + 10y
D. 10x + 5y
15. Which number is equivalent to the expression below? 2 × 12 − 8 ÷ 22 F. 2 G. 4
H. 8 I. 22
Cumulative Assessment
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